1. Field of Invention
The present invention relates to an illumination device and, in particular, to a light emitting diode (LED) device.
2. Related Art
Typically, the conventional LED lamp includes an LED module and a power supply. In order to achieve better conversion efficiency, the series voltage of the LED module is usually adjusted to fit the voltage provided from the power supply so as to minimize the loss in the voltage-dropout conversion. For example, if the power supply is connected to the city electricity, the series voltage of the LED module is preferably adjusted to 220V. However, when the output voltage of the DC terminal of the power supply is larger than 60V (safety voltage), it will be determined as a high-voltage terminal. In order to protect the user from the electric shock caused by the high-voltage terminal, the Standard UL 1598 (UL Lighting Standard) requests the lamp with high voltage higher than the safety voltage to configure an additional safety barrier for isolating and protecting the high-voltage wires. This configuration can prevent the user from directly connecting the high-voltage wires. A conventional LED device configured with the safety barrier will be described hereinafter.
U.S. patent application Ser. No. 11/774,422 discloses an LED apparatus including a mounting board, a plurality of LED packages thereon, a lens member over each LED package, a safety barrier positioned over the mounting board, a resilient member having apertures for each of the lens members, and a cover.
To satisfy the Standard UL 1598, the conventional LED apparatus is configured with the safety barrier on the mounting board for covering the exposed circuits (metal wires) on the mounting board. Accordingly, the safety barrier may contain: (1) iron-contained or iron-free metal with a thickness of at least 0.016 inches; (2) glass or ceramics with a thickness of at least 0.118 inches; (3) glass fiber tube with a thickness of at least 0.010 inches; (4) vulcanized fiber with a thickness of at least 0.028 inches; or (5) polymers with a flame class of HB.
The light emitted from the LED packages is properly distributed through a light-transmission portion of the lens member. The resilient member covering the lens member is made of rubber, so that it can provide the functions of water-proof and dustproof and absorb the heat generated by the LED, which may cause the shift of the lens member.
However, the thickness of the resilient member can directly affect the distance between the lens member and the cover. In face, the thicker the resilient member is, the larger the distance between the lens member and the cover is. When the distance between the lens member and the cover becomes larger, more light beams will be trapped and blocked inside the LED apparatus. Accordingly, the thickness of the resilient member must be properly decreased to increase the light output.
Besides, if the cover is made of metal material, the minimization of the thickness of the resilient member has a critical limitation due to the arcing issue of the cover and the safety barrier.
Therefore, it is an important subject to provide an LED device that is thinner and has lower light loss and higher safety.